Primary Neuroendocrine Tumor of the Sphenoid Sinus: Three Case Reports

Objective: Presentation of three cases of primary intracranial neuroendocrine tumor of the sphenoid sinus, with a review of the most recent literature published.

Method: We report three cases that occurred in our center, with a bibliographic search performed in PubMed using the keywords “neuroendocrine tumor,” “intracranial” and “primary.”

Results: Case 1: A 44-year-old patient presented with headaches over the last 3 months. A MRI of the skull base demonstrated a mass lesion in the sphenoid sinus. An extension study was performed, which was negative. Acromegaly and Cushing's syndrome were also discarded. Biopsy of the lesion was performed, resulting in neuroendocrine tumor with hormonal expression for GH, LH, and HCG.

Case 2: 63-year-old patient presented with pathological visual field. A cranial MRI is performed where a neoplastic mass is seen in the sphenoid sinus suggestive of tumor lesion with aggressive local behavior (Fig. 1). The presence of macroprolactinemia and central hypothyroidism stands out in blood samples. Subtotal resection of the lesion is performed, resulting in low histological grade neuroendocrine tumor.

Case 3: A 60-year-old patient with a history of melanoma and prostate cancer, consulted because of a long-standing headache. A sphenoid sinus mass is seen in cranial MRI. A biopsy is performed with the result of neuroendocrine carcinoma of intermediate degree of malignancy. Given these findings, surgical intervention is performed with macroscopically complete resection.

Conclusions: Intracranial neuroendocrine tumors without evidence of a primary tumor are extremely rare, mostly metastatic from the gastrointestinal tract or respiratory tract. During the past 40 years, 75 cases of small cell neuroendocrine carcinoma of the nasal and paranasal cavities have been reported in the literature.

Therefore, a full body imaging that discards an origin away from the CNS is essential. The radiological findings are not specific, obtaining similar images as in meningiomas, schwannomas, glomus tumor or metastasis. That is why the combination of anatomical and functional techniques is recommended. In this sense, scintigraphy has demonstrated its usefulness for the location of radiologically occult tumors.

Pathological diagnosis is the gold standard. The neuroendocrine tumor must be distinguished from squamous cell carcinoma, melanoma, esthesioneuroblastoma or pituitary adenoma, among others. Synaptophysin and chromogranin A are sensitive but not specific markers, and several immunohistochemical markers must be combined to arrive at the diagnosis.

The malignancy of these tumors is divided into 3 parts, according to the K_i-67 index: under 1–3%; 3–20% medium, >20% high.

The treatment must be multidisciplinary. At present there is no systematic treatment due to its low incidence and the little literature published in this regard, but it seems that surgical resection followed by radiotherapy and chemotherapy treatment is the one with better disease control and overall survival.